Update on o2-sensor Change

[SnakeyesTx]

I had to cave in and drop the exhaust. I borrowed a lift at a friend's shop, swapped the sensor, fired up the car and the check engine light was still on. I hadn't disconnected the battery yet so I figure I'll do it when I get home. Halfway home (about 5 miles into a 10 mile trip) the engine gets up to operating temperature and suddenly the light turns off. I can feel the idle issues disappear at short stops and stop signs, and the acceleration even get better. About a block from my house, I'm sitting at a red light for what seemed like forever, and out of the blue, the motor bucks and the idle bogs down like it used to do, and the check engine light comes back on. It's back to its retarded acceleration too. As I pull into the driveway, the light turned off again and idle went back to nice and smooth, aka normal.

Disconnected the battery for over 2 hours, put it back on, started the car, no light, smooth idle, good drivability again.

First red light I get stuck at for more than 2 minutes, bang.. bog down for a second, idle b/s again, check engine light back on. I pull over and stomp test, and sure enough same 1221 code for o2 sensor. The light came on and off all night at various times after that.

So... wtf? It's only kicking the light on when I have to sit at idle for a while at lights. It eventually goes away after driving a few minutes. Problem is, I have to get the car inspected before the month is out and I can't have that stupid light coming on. Anyone have this issue before?

I replaced the o2 sensor with a Bosch OE replacement (#13108) in case anyone wanted to know what was used.

[Martin in Bellevue]

Is the exhaust tight,any leaks at the manifold? Check the o2 sensor heater relay? Is an exhaust leak allowing the sensor to get too cold for proper output range?
These are guess' based on the probable issues listed for the wideband o2 sensor by Innovate Motorsport.

[Jeff in MN]

I had to cave in and drop the exhaust. I borrowed a lift at a friend's shop, swapped the sensor, fired up the car and the check engine light was still on. I hadn't disconnected the battery yet so I figure I'll do it when I get home. Halfway home (about 5 miles into a 10 mile trip) the engine gets up to operating temperature and suddenly the light turns off. I can feel the idle issues disappear at short stops and stop signs, and the acceleration even get better. About a block from my house, I'm sitting at a red light for what seemed like forever, and out of the blue, the motor bucks and the idle bogs down like it used to do, and the check engine light comes back on. It's back to its retarded acceleration too. As I pull into the driveway, the light turned off again and idle went back to nice and smooth, aka normal.

Disconnected the battery for over 2 hours, put it back on, started the car, no light, smooth idle, good drivability again.

First red light I get stuck at for more than 2 minutes, bang.. bog down for a second, idle b/s again, check engine light back on. I pull over and stomp test, and sure enough same 1221 code for o2 sensor. The light came on and off all night at various times after that.

So... wtf? It's only kicking the light on when I have to sit at idle for a while at lights. It eventually goes away after driving a few minutes. Problem is, I have to get the car inspected before the month is out and I can't have that stupid light coming on. Anyone have this issue before?

I replaced the o2 sensor with a Bosch OE replacement (#13108) in case anyone wanted to know what was used.

and taking it for a test drive. I was checking mine out this week and disconnected it. The CEL came on after a few minutes, but the car drove fine, both at idle and during acceleration. I hooked it back up and the light went out after about a 1/2 mile and the performance was the same. Guess I am saying, see if you get the same problem without 02 sensor hooked up. If the problem appears, I am guessing something else is causing the CEL. Check your temp sensors to make sure they are within spec.

[mangler]

test your fuel pump

[SnakeyesTx]

Where can I find said relay?

[Dave M]

The DME, Fuel Pump and O2 sensor relays are shown in the pic below. Also shown is the switch I made to run the fuel pump to test it.

http://img.photobucket.com/albums/v11/dave_macisaac/Bimmer/Fuel%20Pump/DSC00502.jpg

Dave M

[SnakeyesTx]

Nice! Labeled and all :D Thanks

[SnakeyesTx]

Okay, my relays look a little different than the picture, but I went ahead and changed the one closest to the fender like the one in the picture. It was white and had the number 12.631729004. Started the car, drove it around the block a few times with the CEL off and it ran just fine like before.

As soon as the temperature hit the 1/2 mark, I did the typical "stop for about a minute" simulating being at a red light.

Light came on again, idle fluctuated and the car bucked like it wanted to take off again like before. I can't get the light to come on while driving, only when I come to a stop and sit there for a bit. Sure, my fuel pump makes the typical high pitched noise like a GM one does, but this has really got me stumped. Any other ideas? :(

Stomp Test gave me the 1221 code again.

[SnakeyesTx]

Well, its the last day of the month... gonna drive it till the light turns off then try the inspection. ... failure is eminent though. I hate inspections. Something always tends to go wrong.

[632 Regal]

im sure you have but just incase, have you check real good for intake leaks, cracks in the airbox etc?

[SnakeyesTx]

It actually passed! Light came on again while it was idling on the dyno.. go figure. 1221 again when I checked in the driveway just now. Ah well.. its safe for another year, but I'd still like to know what would trip that. I'll start swapping temp sensors here and there.

[Tiger]

I would say it is your air flow meter. Alot of time the O2 sensor code means something else... not O2. AFM is usually the culprit. Try cleaning it with brake cleaner, carb cleaner or AFM cleaner. Do it with wire disconnected and out of the car to drain out all solvent.